314 FORCING DEPARTMENT. 



ventative for the breakage of glass that has ever 

 come under my observation. The panes are all 

 bedded on a small stripe of solid lead, which is 

 rabbitted on both sides, so as to fit the thickness of 

 the glass, and which prevents it from slipping out 

 of its proper place. The small aperture left in the 

 centre is to carry off the moisture and foul air that 

 collect within the house. 



It has, however, been asserted by many, that 

 metallic substances are less durable than wood in 

 Hot-House Roofs, however well executed. Now 

 this is an assertion, which I really consider too pre- 

 posterous to require any refutation. In the name 

 of common sense, I would inquire, what, prima facie, 

 can render metal materials less durable in Hot-House 

 Roofs than in other buildings, where we meet with 

 fragments still remaining, that have been in use for 

 centuries ; and the same material is introduced 

 daily by all the eminent architects of the age, in 

 the execution of the various buildings which they 

 design, and which they intend shall stand for ages. 



In arguing this question, it is unfair to bring the 

 durability of wood houses, erected in the present 

 day, with those constructed even thirty years ago, 

 as the subject of comparison. Nobody would think, 

 in the present day, of shutting out, by the monstrous 

 bars, then in use, the sun and light. We must 

 take modern wood structures for the standard, and 

 modern metal ones ; and as it is obvious in these, 

 that the wood materials of the roofs have been re- 

 duced to nearly half the substance of those erected 

 forty years ago, their strength and durability must, of 



